Axial flow fan apparatus

ABSTRACT

A vane axial flow fan is shown having a shroud construction which provides greater than normal rigidity in the areas coextensive with the stator vanes and fan wheel blades. These areas of the shroud are formed as metal spinnings to permit unusually deep flanges with well-rounded transition areas to reduce turbulence of the fluid stream passing around them as it passes through the fan. The fan shroud is disposed within a rectangular cage formed of interconnected axially extending and tangentially extending angle bars. The tangentially extending bars are directly connected to the flanges of the fan shroud.

United States Patent 1191 Li evens et a]. [4 Dec. 9, 1975 AXIAL FLOW FAN APPARATUS 2,410,450 11/1946 Kroon 415/219 R 2,717,554 9/1955 Stalker.... 415/210 [75] Inventors Rfmald Onalaska, 3,403,843 10/1968 Cox 415/219 R $9 Kauai Genoa, both of 3,708,242 1/1973 Bruneau et al 415/219 R [73] Assignee: The Trane Company, La Crosse, Primary Examiner 'y Raduazo Wis. [22] Filed: Dec. 23, 1974 [57] ABS CT A vane axial flow fan is shown having a shroud con- [21] PP No.2 535,430 struction which provides greater than normal rigidity in the areas co-extensive with the stator vanes and fan [521 US Cl 415/210; 45/219 417/423 R wheel blades. These areas of the shroud are formed as 51 1111.03 F01D 1/02 metal spiuuiugs Pumut unusually deep flanges with [58] Field of Search 0 417/423 415/2O7 209 well-rounded transition areas to reduce turbulence of 2 /210 the fluid stream passing around them as it passes through the fan. The fan shroud is disposed within a [56] References Cited recgangulardcage formefil of interlc onnected ixiallyTelitten mg an tangentla y exten mg ang e ars. e UNITED STATES PATENTS tangentially extending bars are directly connected to HOSCh R the flanges of the fan shroucL 2,031,688 2/1936 Bowen 417/423 R 2,191,341 2/1940 Curley 415/210 8 l ms, 5 Dr wing Figures atent Dec. 9, 1975 Sheet 1 of 2 3,924,964

US. Patent Dec. 9, 1975 Sheet 2 of2 3,924,964

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AXIAL FLOW FAN APPARATUS A great variety of axial flow fans are known to the prior art. They have been constructed in sizes ranging from fractional horsepower to hundreds of horsepower. Some employ shrouds formed of plural annular U- shaped channel members. On large fans it becomes increasingly important to provide a shroud which is rigid but that uses a minimum of material. Furthermore, the interior of the shroud must be acceptable from an aerodynamic point of view so as not to adversely affect the fan efficiency and noise generation.

It is the purpose of this invention to achieve these objectives. This has been accomplished through the use of a fan shroud comprised of a plurality of specially constructed annular U-shaped channel members or hoops connected at their flanges. The web or cylindrical central portion of the U-shaped members differs in diameter from one member to the next member. In the areas where it has been discovered that greater strength and rigidity are required, the annular members are provided with substantially smaller diameter webs with substantially greater. flange depths. In areas requiring less rigidity channel members having substantially reduced flange depth and increased web diameter are provided. The outer diameter of the flanges of both types of channel members are the same so they may be readily interconnected. Furthermore, the fan shroud is disposed within a rectangular cage which supports the flanges of the annular channel members.

More specifically this invention involves an axial flow fan including a shroud having: a first annular channel member of U-shaped cross section having a substantially circular axially extending first web disposed intermediate first and second radially outwardly extending flanges; a second annular channel member of U-shaped cross section having a substantially circular axially extending second web disposed intermediate first and second radially outwardly extending flanges; a third annular channel member of U-shaped cross section having a substantially circular axially extending third web disposed intermediate first and second radially extending flanges, said first and second webs being of a diameter less than the diameter of said third web, said third channel member being disposed axially intermediate said first and second channel members in co-axial flange-to-flange facing relationship; and means for fixedly connecting the adjacent facing flanges of said first and third and said second and third channel members.

Thus it will be seen that through the use of a very specialized fan construction, both the desired rigidity and minimum use of material can be achieved to provide a higher quality of fan at reduced cost.

These and other objects of the invention will become more apparent as this specification proceeds to describe the invention with reference to the drawings in which:

FIG. 1 is a side elevation of an axial flow fan containing the invention herein described;

FIG. 2 is an end elevation showing the inlet end of the fan shown in FIG. 1;

FIG. 3 is a vertical sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a vertical sectional view taken near the outlet end of the fan at line 44 of FIG. 3; and

FIG. 5 is a vertical section taken substantially through the center of the stator vane portion of the fan showing the bearing support and drive mechanism.

Now with reference-to the drawings it will be seen that the axial flow fan 10 includes a fan shroud or housing 12 disposed within a cage 14 constructed of angle iron bars.

A fan wheel 16 is mounted with the fan shroud 12 near the inlet end thereof. Fan wheel 16 is provided with a plurality of circumferentially spaced radially outwardly extending airfoil blades 18. Fan wheel 16 is fixedly mounted on shaft 20 for rotation therewith. The fan wheel 16 is further provided with a rounded nose piece 22 for efficiently directing air or other fluid to the fan blades.

A stator core 24 of generally circular cylindrical configuration is disposed immediately downstream of fan wheel 16. At the downstream portion of the stator core there is provided a plurality of circumferentially spaced stator vanes 26 which extend radially outwardly from stator core 24 to the shroud 12. The vanes 26 are welded at each end whereby the stator core is supported by shroud member 12.

' Shaft 20 extends from the inlet end of shroud 12 to a point rearwardly of i.e., downstream of stator vanes 26. The forward end of shaft 20 is rotatably supported by way of a forward bearing bracket 28 which is preferably constructed in accordance with the teachings of US. Pat. No. 3,403,843. The rear portion of shaft 20 is rotatably mounted within a bearing supported by a rear bearing bracket 30 rigidly connected to the interior of stator core 24. The rear end of shaft 20 is provided with a sheave 32 drivingly connected to motor 34 via belts 36 which extend through an openings 38 in shroud l2 and 39 in stator core 24. The downstream side of stator core 24 is preferably closed by way of an end bell 40. Motor 34 is preferably mounted on cage 14.

Cage 14 is constructed of several square frames 41 each having four tangentially arranged angle bars 42 connected to each other at their ends as at 44. The several frames are interconnected by a longitudinally extending angle bar 46 passing just inside each corner of the square frame. Connections are preferably made by welding. The tangentially extending bars 42 and axially extending bars 46 provide a support cage for shroud 12 as will be hereinafter described.

Shroud 12 is comprised of five annular channel members of U-shaped cross section each having a cylindrical substantially circular web disposed intermediate radially outwardly extending flanges. A first annular channel member 50 is disposed primarily in the vincinity of the fan wheel 16 and is axially co-extensive therewith. A second annular channel member 52 is disposed primarily in the vicinity of stator vanes 26 in axially co-extensive relationship therewith. A third annular channel member 54 bridges between channel members 50 and 52. A fourth annular channel member 56 extends forwardly or upstream of annular channel member 50 and the fifth annular channel member 58 extends rearwardly or downstream of annular channel member 52. The flanges of all of the channel members 50, 52, S4, 56, and 58 all have substantially the same outer diameter. However, the flanges of annular channel members 50 and 52 are substantially deeper than those of channel members 54, 56, and 58. The webs of channel members 50 and 52'are of equal diameter and of substantially less diameter than the webs of channel members 54, 56, and 58. In the embodiment shown the webs of channel members 54, 56, and 58 are of equal diameter. Furthermore, it will be noted that the transition portion of the flanges on channel members 50 and 52 have a very large radius of curvature as seen in FIG. 3 so as to avoid excessive turbulence within the shroud 12. The increased depth of the channel of each of members 50 and 52 thus provides a relatively greater rigidity in critical areas of the fan. The radius of curvature of a transition areas of channel members 50 and 52 is between 0.01 and 0.1 times the diameter of the web portion thereof. The radius of curvature of the transition area of the flanges of channel member 54 are less than 0.01 times the diameter of the web thereof.

In order to achieve this unique channel configuration and relationship, it is preferred to form channel members 54, 56, and 58 by roll forming at low cost and to form channel members 50 and 52 by spinning whereby transition areas of sufficiently large radius of curvature may be formed.

The fan shroud is supported with and by cage 14 heretofore described. The plane of each frame 41 of the four tangentially extending angle bars 42 is positioned adjacent and welded as at 60 directly to flanges of the U-shaped channel members. In the embodiment shown having five support frames, the shroud 12 may be supported at sixteen spaced points by cage 14. If corner braces 62 are employed on each frame, the number of support points can be doubled.

It will thus be seen that relative shape and position of U-shaped channel members 50, 52, 54, 56, and 58 disposed within, and supported at multiple spaced points provides an unusually strong and light fan construction. The substantially more rigid member 50 permits closer blade tip clearance while the substantially more rigid member 52 provides ample support for the rear bearing through the stator core and vanes. The large radius on the flanges of members 50 and 52 efficiently direct the fluid flow to and from the fan blades and stator vanes.

Although we have described a specific embodiment of our invention, it is contemplated that various changes may be made without departing from the spirit of our invention, and we desire to be limited only by the claims.

We claim:

1. An axial flow fan including a shroud having: a first annular channel member of U-shaped cross section having a substantially circular axially extending first web disposed intermediate first and second radially outwardly extending flanges; a second annular channel member. of U-shaped cross section having a substantially circular axially extending second web disposed intermediate first and second radially outwardly extending flanges; a third annular channel member of U-shaped cross section having a substantially circular axially extending third web disposed intermediate first and second radially extending flanges, said first and second webs being of a diameter less than the diameter of said third web, said third channel member being disposed axially intermediate said first and second channel members in co-axial flange-to-flange facing relationship; and means for fixedly connecting the adjacent facing flanges of said first and third and said second and third channel members.

2. The axial flow fan as defined by claim 1 further including an axial flow fan wheel having circumferentially spaced radially outwardly extending blades disposed in axially co-extensive relationship with said first web.

3. The axial flow fan as defined by claim 2 further including a plurality of circumferentially spaced stator vanes extending radially inwardly of said second web; and a centrally disposed diffuser core spaced radially inwardly of and axially co-extensive with said second and third webs.

4. The axial flow fan as defined by claim 3 further including means for rigidly fastening said stator vanes at their radially outer ends to said second web and their radially inner ends to said core.

5. The axial flow fan as defined by claim 4 further including a rotatable shaft; means fixedly mounting said fan wheel to said shaft for rotation therewith; bearing means disposed radially inwardly of said core for rotatably supporting said shaft; and bearing support means including said stator blades and said second web for supporting said bearing means.

6. The axial flow fan as defined by claim 1 further including a rectangular shroud support cage disposed about said shroud including a plurality of axially extending support bars and a plurality of tangentially extending support bars fixedly connected to each other; and means directly fixedly connecting at least some of said annular channel flanges to said tangentially extending support bars.

7. The axial flow fan as defined by claim 1 wherein the transitions between the web and flanges of said first and second channel members have a radii of curvature greater than 0.01 times the diameters of said first and second webs respectively and the transition between the web and flanges of said third channel member has a radius of curvature less than 0.01 times the diamter of said third web.

8. The axial flow fan as defined by claim 7 wherein said first and second channel members are metallic spinnings and said third channel member is a rolled annulus. 

1. An axial flow fan including a shroud having: a first annular channel member of U-shaped cross section having a substantially circular axially extending first web disposed intermediate first and second radially outwardly extending flanges; a second annular channel member of U-shaped cross section having a substantially circular axially extending second web disposed intermediate first and second radially outwardly extending flanges; a third annular channel member of U-shaped cross section having a substantially circular axially extending third web disposed intermediate first and second radially extending flanges, said first and second webs being of a diameter less than the diameter of said third web, said third channel member being disposed axially intermediate said first and second channel members in co-axial flange-to-flange facing relationship; and means for fixedly connecting the adjacent facing flanges of said first and third and said second and third channel members.
 2. The axial flow fan as defined by claim 1 further including an axial flow fan wheel having circumferentially spaced radially outwardly extending blades disposed in axially co-extensive relationship with said first web.
 3. The axial flow fan as defined by claim 2 further including a plurality of circumferentially spaced stator vanes extending radially inwardly of said second web; and a centrally disposed diffuser core spaced radially inwardly of and axially co-extensive with said second and third webs.
 4. The axial flow fan as defined by claim 3 further including means for rigidly fastening said stator vanes at their radially outer ends to said second web and their radially inner ends to said core.
 5. The axiaL flow fan as defined by claim 4 further including a rotatable shaft; means fixedly mounting said fan wheel to said shaft for rotation therewith; bearing means disposed radially inwardly of said core for rotatably supporting said shaft; and bearing support means including said stator blades and said second web for supporting said bearing means.
 6. The axial flow fan as defined by claim 1 further including a rectangular shroud support cage disposed about said shroud including a plurality of axially extending support bars and a plurality of tangentially extending support bars fixedly connected to each other; and means directly fixedly connecting at least some of said annular channel flanges to said tangentially extending support bars.
 7. The axial flow fan as defined by claim 1 wherein the transitions between the web and flanges of said first and second channel members have a radii of curvature greater than 0.01 times the diameters of said first and second webs respectively and the transition between the web and flanges of said third channel member has a radius of curvature less than 0.01 times the diamter of said third web.
 8. The axial flow fan as defined by claim 7 wherein said first and second channel members are metallic spinnings and said third channel member is a rolled annulus. 